On Mon, Feb 29, 2016 at 8:56 AM, Geoff Winkless <pgsqladmin@xxxxxxxx> wrote:
I'm sure I'm missing something here.
A query takes 50 seconds; it's doing a seq-scan on a joined table,
even though the table is joined via a field that's the leftmost column
in a multicolumn index
(http://www.postgresql.org/docs/9.5/static/indexes-multicolumn.html
says "equality constraints on leading columns ... will be used to
limit the portion of the index that is scanned")
http://explain.depesz.com/s/suv
If I create an individual index on just the linked key, the explain
shows the index being used and the query takes 1.7s.
http://explain.depesz.com/s/b9ZS
Now here's the odd bit:
SET effective_cache_size TO '2146435072'
causes the index to be used.
SET effective_cache_size TO '2047MB'
causes it to use tablescan. Shouldn't those two be equivalent?
No they are not the same. When you don't include a unit for effective_cache_size, it defaults to page size so you're saying 2146435072 * 8K
Is
there a blowup in the planner checking effective_cache_size value not
expecting the human-readable value?
Thanks for suggestions
Geoff
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